Improved method of shooting wells



JOHN J. GBEBE AND NOLAND POFFENBERGER, OF MIDLAND, MICHIGAN, ASSIGNQRS TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN Ho Drawing. Application filed June 4,

Our invention relates to the art of shooting brine, oil, gas, and other wellswith an explosive such as nitroglycerin which is frequently done for the purpose of improving or increasing the yield of the well and relates specifi cally to a method of protectingthe well casing and the walls of the bore from damage by shooting.

Aside from the above-ground danger to property, life, and limb, in handling high explosives, the actual shooting of the well is frequently accompanied by damage to the walls of the bore followed by spalling and caving, or if the casin be not removed, splitting and/0r collapsing of the casing. In shooting brine wells,-for instance,- to improve the yield of flow of brine, it has been customary to lower into the well a charge of nitroglycerin, locate the charge in the brinerock, and there explode it." The well will normally be filled either entirely or partially with water or brine, the inertia of which is, of course, a factor in directing or controlling the work done by the explosive upon the rock. It has been found that serious damage may be done to the well by shooting and in many cases wells have been lost because of damage by shooting. It is customary after the 'explosion of the charge to bail the well to remove dbris and clean out the hole, but it is not in all cases possible to bail the well, since caving or spalling may have closed the hole.

If the casing be wholly'or partly filled with brine or water and left in the well when it is shot, such casing may be split or collapsed in which'case the removal and resetting of thecasing is attended by serious risks ofloss of the well. In many cases the cleaning out operation following a shooting has been both disappointing and expensive and there a are many wells which have had to be abandoned following shooting and sometimes after the loss of several. strings of tools in the hole.

The removal of a casing prior to shooting is also a risky proceeding, since it may be difiicult or impossible to reseat it after the shot.

It is accordingly highly desirable that a method be worked out which will permit the safe .mshgotin'g of a well without damagingthe casing insitu'even though it be partly or en- IMPROVED METHOD OF SHOOTING WELLS 1930. Serial No. 459,257.

of the steps hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail one mode of carrying out the invention, such disclosed mode illustrating, however, but one of various ways in which the principle of the invention may be used,

Conceiving that the damage to the hole and/or the casing is due tothe compressional wave traveling up the bore of the hole, we have directed our efforts to cushioning the shock exerted by such awave upon the walls confining it. ,We introduceintothe-water, oil, brine, or liquid filling the well a gas, either in the form of a relatively large gas-filled space or spaces, or in the form of bubblesmore or less distributed. The presence of such gas I in the well introduces a shock absorbing element which cushions the effect of the compressional wave upon the walls confining it,

such as the bore in the rock and/or the casing.

In order to so introduce a gas we may proceed in a number of ways. For example (1) we may employ the action of acids on car onates to liberate carbon dioxide gas in situ, (2) the action of sodium, calcium, potassium, or like metals upon water by means of which hydrogen gas is liberated, (3) the action of water on carbides? such as calcium carbide, to liberate acetylene in situ, (4) introduction of compressed gases, such as an or natural gas or t e like, by mean of a tube lowered into the well, (5) introduction of low boiling point liquids which may be released from a cylinder in situ, (6) introduction of so-called dry ice, i. e. solid carbon dioxide, lowered into the hole where itwill 'gasify spontaneously.

lVe may also use emulsifying agents in col- 9 loidal substances, such as soap, foamite, glue, andthe like by adding same to the liquid in the well to improve the action of the gas introduced, such agents acting to hold the gas dispersed in the liquid qontained in the well.

Although, as indicated above, there are many ways in which a gas may be introduced for the purpose of cushioning the compressional wave, we have found the use of dry ice a convenient and practicable method. After the introduction of the nitroglycerin cartridge and the completion of preparations to shoot, a quantity of solid carbon dioxide may be dropped into the hole, and depending upon the depth of water, brine, or other liquidtherein, sufiicient time will be allowed for the solid carbon dioxide to fall through the brine" or other liquid to a point in the well preferably above but relatively near the explosive charge. By observing the rate offall of carbon dioxide experimentially in a tube filled with liquid from the hole such time factor may be fi ured out. After the calculated time has e apsed we shoot the charge in the customary way.

Example In a salt brine well bored to a depth of 1290 feet into and through a porous sandstone stratum approximately 100 feet in thickness constituting the brine rock, the

bore of the holein the brine rock being approximately 8 inches and 1085 feet of 8 inch casing standing, in the hole; a charge of 500 quarts of nitroglycerin was lowered into the well. The .brine 'rose in the hole to an approximate depth of 840 feet measured above the brine rock stratum. When preparations had been completed for shooting 150 pounds of dry ice, i. e. solid carbon dioxide in lump form was dropped freely into the hole in 2 minutes, time and after a lapse'of 5 minutes from. completing introduction, the charge was shot. The contents of the well were discharged with considerable force following the ground shock usually experienced, but it into the brine protected the bore of the well and the casing from -damage. The fact that a heavy charge was used in a well containing a heavy salt brine, without removing the casing, without damage to the well .or'casing provesthe efficacy of the method.

The shooting'of other lwells, such as oil' or water wells, will follow along the lines of the above example, it being obvious that although a general plan will be followed in cases,

due regard .shouldbe given to depth, head of liquid and weight thereof in the hole, the capacity of the liquid to absorb the gas introduced, and the, character of gas used and the methods employed to introduce same. By' whatever method the; gas is introduced'or' whatever gas be so introduced, the effect will .in all cases beto. cushion the shock upon the walls of the well andupon the casingof the compressional wave traveling up the well from the exploding charge and by reason of such cushion to avoid damage to an otherwise vulnerable bore or casing or to so reduce the damage upon the bore as not to seriously interfere with the cleaning operation and further use of the well.

Many variations of methods and means to introduce the gas cushion will be 0 vious to those skilled in the arts, among wh' h may be mentioned the following. In ord r to hmit the depth to which the gas producing ingredients shall penetrate in thewell we have found that'a stock plate may be inserted-conveniently in the form of a metal disc with a central hole through which the cable suspending the explosive passes. Such a disc will catch and arrest the gas generating material and thereby the depth at which gas generation proceeds. Such a disc may rest upon the cartridge containing the explosive or may be afiixed to the suspending cable at any point thereon. Another method involves the use of a thin cylinder, such as can be formed of sheet metal closed at the top. and suspended-from a wire or light cable.

'Such a cylinder will be open at the bottom but provided at such opening with a' grate or screen. The gas generating material such as carbide or dry ice may be inserted into this cylinder, which on account of its weight characteristics, may be rapidly lowered-into the well to any desired depth therein. The

gas evolved will bubble out from the open lower end of the cylinder and be introduced into the liquidin the well.

- Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided. the step or steps stated by any of the following claims or the equivalent of such stated step or steps beemployed.

We therefore particularly point out and :distinctly claim as our invention:

1.'*The method of shooting a deep well while materially reducing the damage thereby tothe walls of the well (includin a cas ing if present) above the stratum to e shot when the well contains a liquid, which come prises placing a charge of explosive in the well, bringing about the presence in theliquid above the said charge of a gaseous medium to cushion the effect upon. said walls of the compression wave transmitted therethrough following the explosion of charge and exploding the charge.

2. The method of shooting a deep well while materially reducing the damage therethe by to the walls of the well (includin a, casing if present) above therstratum to e shot when the well contains a liquid, which comprises placinga charge of explosive in the well, bringing about the presence in the liq-.-

uid above the said charge of CO gas to cushion the effect upon said walls of the compression wave transmitted therethrough fol-' lowing the explosion of the charge and exploding the charge.

3. Themethod of protecting a well casing in .situ in a well from substantial damage when shooting such well by exploding acharge of explosivein the bore thereof below said casing when said well contains a liquid extending up into, said casing, which comprises bringing about the presence in the.

liquid above the charge of a gaseous medium to cushion the efi'e'ct upon'said casing of the compression wave transmitted therethrough followin the explosion of the charge, and then exp oding the charge.

4. In a method of shooting a bored well containing a casing in situ and a liquid in' said bore extending into 881d casing wh1le substantially avoiding damage to said casing, the steps which-consist in placing an explosive charge in" the bore below said casing, bringing about the presence of'a cushion of a gaseous','medium' in the liquid above] said char e, and then explodin the char e.

i 5. na method of shooting a-bore well containing a casing in'situ and a liquid in said bore extending into said casing while substantially avoiding damage to said casing,

the steps which consist in introducing an explosive charge into said bore below said casing, introducing then into the liquid above bore above the charge is; at least materially" reduced through the cushioning action of said' gaseous mediuni upon the compression wave transmitted through the liquid from the exploding charge.

' 7=,The method of, shooting, a .deep well ,containing liquid which comprises placing an explosive charge in the bore at the elevation therein at which it is desired to. concentrate the efiect of the shot introducing solid carbon doxide into the liquid to generate transmitted through the liquid from the exploding charge.

8. The method of confining the destructive effect of the explosion of a charge of explosive in a deep well containing liquidsubstantially to that portion at or below the limit at which the explosive is located which comprises placing the charge in the well at an elevation therein corresponding to the zone to be affected by the shot, introducing a gaseous medium into the liquid in the well above the shot to cushion the effect of the compression wave transmitted from the shot through the liquid, and'exploding the charge. Signed by us this 2nd day of June, 1930. JOHN J. GREBE. NOLAND PQFFENBERGER therein a cushion of carbon'dioxide gas, and

exploding the chargerwhereby damage to the walls of the-bore above the charge is at least materially reduced through the action of said cushion uponthe compression wave 

